The present invention generally relates to lancing devices for lancing dermal tissue and for withdrawing a fluid sample.
Lancets in conventional use generally have a rigid body and a sterile needle which protrudes from one end. The lancet may be used to pierce the skin, thereby enabling the collection of a blood sample from the opening. The blood is then transferred to a test collection device. Blood is most commonly taken from the fingertips, where there is generally an abundant supply. However, the nerve density in this region causes significant pain in many patients. Sampling of alternate sites, such as earlobes and limbs, is sometimes practiced to access sites which are less sensitive. These sites are also less likely to provide sufficient blood volume, and make blood transfer directly to test devices difficult.
Repeated lancing in limited surface areas (such as fingertips) results in callous formation. This leads to increased difficulty in drawing blood and increased pain to the user. To reduce the anxiety of piercing the skin and the associated pain, many spring loaded devices have been developed.
After puncturing the skin, conventional lancing devices are laid down and the free hand of the user squeezes blood from the puncture wound. This technique requires a clean storage site for the lancing device and a two-hand operation. Once the drop of blood is expressed from the lancing site, the user transfers the blood to a test strip of a suitable meter.
It is often desirable to collect the expressed sample from the patient and then introduce the sample to a test device in a controlled fashion. Some blood glucose monitoring systems, for example, require that the blood sample be applied to a test device which is in contact with a test instrument. In such situations, bringing the finger of a patient directly to the test device poses some risk of contamination from blood of a previous patient. With such systems, particularly in hospital settings, it is common to lance a patient, collect a sample in a micropipette via capillary action and then deliver the sample from the pipette to the test device.
However, these lancet devices do not extract (xe2x80x98squeeze outxe2x80x99) a sufficient sample from the various surfaces for lancing. For example, the curved surface of a fingertip requires the right amount of pressure to be applied to extract blood quickly and efficiently from the patient. Therefore, there is a need for a lancet system that can accommodate the lancing of curved surfaces (e.g., fingertips) as well as flat surfaces (e.g., forearm or leg) to express sufficient volume of blood or interstitial fluid, while concomitantly reducing pain experienced by the user.
The present invention provides a cap for a lancing device for lancing dermal tissue. The cap includes a cap body having a proximal end for connecting to the distal end of the housing of the lancing device and a contact ring attached to the distal end of the cap body. The contact ring includes an opening for a portion of the lancet of the lancing device to pass therethrough. The contact ring has a multi-contoured surface oriented generally about an axis distinct from the axis of motion of the lancet. The multi-contoured surface is designed to pressure the dermal tissue to facilitate expression of a fluid sample after lancing the dermal tissue. The fluid sample can include blood, interstitial fluid, or both.
In accordance with one aspect of the present invention, the cap body is transparent to facilitate viewing of the quantity of blood expressed.
In accordance with another aspect of the present invention, the multi-contoured surface comprises an outer radial portion oriented at a first angle relative to the axis of the contact ring and an inner radial portion proximate the opening and oriented at a second angle, distinct from the first angle, relative to the axis of the contact ring.
In accordance with a further aspect of the present invention, the cap is removably and replaceably connected to the distal end of the housing.
In accordance with another aspect of the present invention, a sleeve can be mounted about the cap body. The sleeve can be movable generally along the axis of motion of the lancet and relative to the cap body. The sleeve includes at least two legs for maintaining contact with the dermal tissue during expression of a blood sample after lancing the dermal tissue. In addition, the sleeve can be biased toward the distal end of the cap body, for example, by a spring.
In accordance with another aspect of the present invention, the cap body includes a contact ring having a multi-contoured surface oriented to create a radially inwardly extending pressure-gradient, which extends towards a central aperture.
In accordance with another aspect of the present invention, a cap for lancing curved dermal tissue is provided. The contact ring portion of the cap is comprised of a flexible material. The flexible material when placed against the lancing site conforms to the surface, and hence accommodates lancing of the curved dermal tissue to create a pressure gradient beneath the skin to express a suitable fluid sample. This flexible cap creates a pressure gradient and expresses dermal fluid on strongly curved and flat areas of the skin without having to change the cap or use a different lancing device.
In accordance with yet another aspect of the present invention, a lancing device for lancing dermal tissue is provided. The lancing device includes a housing, a lancet and a cap. The cap includes a cap body and a contact ring having a multi-contoured surface oriented generally about an axis distinct from the axis of motion of the lancet. The multi-contoured surface is designed to pressure the dermal tissue to facilitate expression of a fluid sample after lancing the dermal tissue. The fluid sample can include blood, interstitial fluid, or both.